Housing for gas sensors

ABSTRACT

A housing (5) gas sensors, preferably lambda probes for detecting the content of pollution or oxygen or both in exhaust from, preferably, internal-combustion engines. A protective outer housing has electric connections at one end for a sensor mounted on a metal. A perforated protective cap accommodates the sensor and is intended for exposure to the gas being analyzed at the other end. A ceramic shape accommodates the connections and/or the metal and is accommodated in turn in the outer housing. The ceramic shape consists of at least two halves with a slot that is open along one side at the first end and with contacts resting flat against the base and walls of the slot with one side elevated above the open side. Each half also accommodates a depression extending all the way to the other end with the metal fitting into the depressions. At least the projecting areas of the contacts are in the vicinity of the depression. The connections are on the back of the contacts.

BACKGROUND OF THE INVENTION

The present invention concerns a housing for gas sensors.

Such a housing is known from German 3 410 122 A1.

One drawback to the known housing is its many separate components, whichmake it complicated and hence expensive to assemble. Although it doesinclude a two-part ceramic shape, it is divided along a planeperpendicular to the axis of the overall housing. The housing mustaccordingly be assembled axially. The contacts are slipped over theplate-like member, producing a notching effect and the risk of damagingthe metal, which the actual sensor is mounted on. The many structuresrequired for securing the plate-like member and the separate electricconnections also contribute to the complexity of assembly.

SUMMARY OF THE INVENTION

The object of the present invention is accordingly to make a generichousing for gas sensors as recited in the preamble to the major claimsimpler and easier to assemble.

The object is surprisingly attained in accordance with the invention ina generic housing as recited in the preamble to the major claim by thecharacteristics recited in the body of that claim.

A housing with a ceramic shape consisting of preferably only two similarhalves is simpler to manufacture. The plate-like member is insertedbetween the halves and the contacts into the open slots. The halves are,in contrast to the state of the art, joined radially and are insertedinto the housing in that state. There are no such relative motions asforcing the contacts over the plate-like member in accordance with thepresent invention. The risk of damage during assembly is accordinglyminimized. The result is a simple and easy-to-assemble housing and verylittle waste.

To eliminate errors due to outside air entering either such apressurized environment as an exhaust pipe or such an evacuatedenvironment as the flue in a heating system or analysis tube, the actualdetection point, specifically the front of the plate-like member, issealed off gas tight from the rear of the housing. It is preferred toestablish the seal from outside by way of a contact between two conicalsealing surfaces. The seal can be further tightened with additionalsealing lips or annular seals or both to force the convex conicalsurface against the concave conical inner surface of the threadedbushing. The tightness between the cone and the plate-like member can befurther increased by cement or glazing or by packing the convexity with(ceramic) powder, preferably in funnel-shaped depressions near where theplate-like member to be accommodated emerges.

It is of particularly great advantage to test and assemble the not yetcompletely finished gas sensor without disturbance from electricconnections in the form of cables. It is also possible to provideconnections in accordance with each customer's specific needs,simplifying maneuvering and adaptation to his specific application. Thehousing can then be finally assembled subsequent to preliminary assemblyand testing in that the areas of the contacts extending beyond one sideof the housing half, integrated along with the electric connections intoa plug, are thrust over or into a separate protective housing with asocket on separated connecting cable. The product can then be finishedby either the manufacturer or the customer once the probe has beeninserted. The separated protective housing can then be manufactured withthe protective housing already in place, by for example snapping,welding, or screwing it together, by securing it with specially designedclips, or otherwise.

Advantageous embodiments and advanced versions of the invention arerecited in the subsidiary claims.

BRIEF DESCRIPTION OF THE DRAWINGS

One preferred embodiment of the invention will now be specified withreference to the drawing, wherein

FIG. 1 is a schematic longitudinal section through one embodiment of thehousing with the contacts in place and with a sensor resting on theplate-like member,

FIG. 2 is a schematic top view of the ceramic shape from FIG. 1,

FIG. 3 illustrates one of the contacts illustrated in FIG. 1, and

FIG. 4 is a partially broken away schematic cross sectional view showinganother embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The gas-sensor housing 5 illustrated in FIG. 1 is accommodated in aprotective outer housing 6. At one end of outer housing 6 are electricconnections 7 leading to the sensor. The unillustrated sensor is mountedon a plate-like member 8. The other end of plate-like member 8, the endwith the sensor, is accommodated within a perforated protective cap 9.Cap 9 is exposed to the gas being analyzed. Outer housing 6 alsoaccommodates a ceramic shape 10 that in turn accommodates connections 7and plate-like member 8.

The ceramic shape 10 in the present embodiment comprises two similarhalves 11. One half 11 is viewed in FIG. 2 along the plane ofseparation, which is identical with the plane of projection. There areslots 12 in this surface at one end 15 of half 11. One side of the slotsis open. An electric contact 13 like the contact illustrated in FIG. 3is inserted in each slot 12. Contacts 13 rest flat against the base andwalls of the slots with one side elevated above the open side.

Each half 11 also accommodates a depression 16 extending all the way toend 14, the end opposite end 15. Plate-like member 8 fits intodepressions 16.

At least the areas of contacts 13 that project beyond the end 15 of half11 are in the vicinity of depression 16. Plate-like member 8 is clampedbetween the depressions 16 in the two halves 11 that constitute ceramicshape 10. The sensor on plate-like member 8 is electrically connected. Asimple electric connection is established by connecting, preferablycrimping, connections 7 to contacts 13. It is of particular advantagefor the contacts to be rest against each side of plate-like member 8,providing a number of adjacent contacts and hence electric connections7. Each side of the metal will accordingly simultaneously be subject touniform mechanical stress.

The two identical halves 11 of ceramic shape 10 are secured stationaryby outer housing 6, which is in the form of a metal sleeve. Each half 11has a contact surface (along the plane of projection of FIG. 2). The twocontact surfaces secure both plate-like member 8 and contacts 13 betweenthem in the assembled product. There is an adhesive accommodation 17 inthe form of a sink in the vicinity of depression 16 and outside thevicinity of the slots. Each half 11 also has assembly guides 18 that fitinto matching depressions on the other half. It is of advantage for theprotective outer housing 6 to accommodate a holder for holding togetherthe two halves 11 of ceramic shape 10. The holder can be a resilientring, or a slotted or shrunk-on sleeve.

Housing 5 has screw-in bushing 21 with a thread 20. Cap 9 extends out ofbushing 21. Outer housing 6 is secured to bushing 21, preferably weldedto area 22.

A socket 24 is preferably attached to outer housing 6 by way of a stack23 of springs. Connections 7 connect to contact 13 by way of a plug 25that fits into socket 24. Outer housing 6 can also accommodate socket24. It is, however, alternatively possible to provide another protectivehousing 60, folded, welded, or cemented to the actual outer housing 6 atan area 26.

The areas of contact 13 that extend beyond the end 15 of half 11 make itpossible to test, assemble, and otherwise finish the sensor withoutinterference from connections in the form of cables. The process willaccordingly be simpler. Only at the very end will socket 24 and plug 25be inserted and connected and separate protective housing 60 secured toouter housing 6.

Each contact 13 has a reversed projection 27 elevated above the openside of slots 12. Projection 27 is rendered resilient by a more or lessarched stamped-out area 28. The resilience can alternatively be derivedby slitting the area of contact 13. Contact 13 is also secured in slot12 by a stamped-out notch 29 engaged by a projection 30 on each half 11of ceramic shape 10.

This embodiment of the housing can be varied even further. The twoceramic halves for example need not be identical but just similar andcan be secured together by an annular holder. A cone can also be securedto the other end of the ceramic shape and rest against a matchingconcave surface in the screw-in bushing to keep contaminating outsideair away from the detection site under the protective cap. Afunnel-shaped depression where plate-like member 8 emerges at each endof the cone is also practical. The depressions allow gas-tightconnection by cementing or glazing, or by packing with (ceramic) powderand stuffing.

The cone can also be connected to the ceramic shape by a spacing sleeve.

The contact can also be produced not by stamping but by bending a pieceof spring steel. The contact can rest on a shackle against projection 30in the slot 12 in half 11. The end of an electric-connection sleeverests against the other side of projection 31 and prevents contact 13 asa whole from sliding back and forth in slot 12.

We claim:
 1. A housing for gas sensors having lambda probes fordetecting the content of pollution or oxygen or both in exhaust frominternal-combustion engines, comprising: a protective outer housing withelectric connections at one end thereof for a sensor mounted on aplate-like member; a perforated protective cap at the other end of saidprotective outer housing and accommodating said sensor for exposure to agas being analyzed; a ceramic shape holding means for securing to saidelectric connections; said ceramic shape comprising at least two halves,each of said halves having a slot at said one end of said outer housing;contacts resting flat against a base and walls of each said slot withone side elevated above an open side; each half of said ceramic shapealso accommodating a depression extending from said one end to saidother end of said protective outer housing; with said plate-like memberfitting into the depressions of said two halves of said ceramic shape;at least projecting areas of said contacts being in said depression,said connections being connected to said contacts.
 2. A housing asdefined in claim 1, wherein said outer housing is a sleeve ofheat-stable material.
 3. A housing as defined in claim 2, wherein saidheat-stable material is metal.
 4. A housing as defined in claim 1,wherein said two halves of said ceramic shape are similar.
 5. A housingas defined in claim 4, wherein each half of said ceramic shape has acontact surface; the two contact surfaces accommodating said plate-likemember and said contacts in said housing between them.
 6. A housing asdefined in claim 1, wherein said two halves of said ceramic shape areidentical.
 7. A housing as defined in claim 1, wherein each half of saidceramic shape has assembly guides for said plate-like member and forsecuring the halves of said ceramic shape.
 8. A housing as defined inclaim 7, said assembly guides on one said half fit into matchingdepressions in the other half once the housing has been assembled.
 9. Ahousing as defined in claim 1, wherein the two halves of said ceramicshape are secured together by an annular holder.
 10. A housing asdefined in claim 9, wherein said annular holder is a resilient ring. 11.A housing as defined in claim 9, wherein said annular holder is aslotted sleeve.
 12. A housing as defined in claim 9, wherein saidannular holder is a shrunk-on sleeve.
 13. A housing as defined in claim1, wherein each of said contacts has a reversed connections area with anadjacent contact area.
 14. A housing as defined in claim 13, whereinsaid contact area comprises a projection projecting beyond the open sideof said slot and being resilient in a part of the contact area.
 15. Ahousing as defined in claim 13, wherein said contact area is resilient.16. A housing as defined in claim 1, wherein said slot has at least oneprojection from said halves on said base for securing said contact witha stamped out notch.
 17. A housing as defined in claim 1, wherein saidslot has at least one projection from said halves on said base forsecuring said contact with a shackle.
 18. A housing as defined in claim1, wherein said outer housing is connected to a separate housing.
 19. Ahousing as defined in claim 1, wherein the housing has a screw-inbushing for securing said gas sensor to said housing and foraccommodating said protective cap, said bushing having a thread.
 20. Ahousing as defined in claim 19, wherein said outer housing is secured tosaid bushing.
 21. A housing as defined in claim 19, wherein one of saidhalves has at said other end a cone secured tight to a matching concavesurface inside said bushing.
 22. A housing as defined in claim 21,wherein said cone has depressions at each end where said plate-likemember emerges.
 23. A housing as defined in claim 22, wherein saiddepressions are funnel shaped.
 24. A housing as defined in claim 21,wherein said two halves and respective cone are secured by an annularholder.
 25. A housing for gas sensors having lambda probes for detectingthe content of pollution or oxygen or both in exhaust frominternal-combustion engines, comprising: a protective outer housing withelectric connections at one end thereof for a sensor mounted on aplate-like member; a perforated protective cap at the other end of saidprotective outer housing and accommodating said sensor for exposure to agas being analyzed; a ceramic shape holding means for securing to saidelectric connections; said ceramic shape comprising two halves, each ofsaid halves having a slot at said one end of said outer housing;contacts resting flat against a base and walls of each said slot withone side elevated above an open side; each half of said ceramic shapealso accommodating a depression extending from said one end to saidother end of said protective outer housing; with said plate-like memberfitting into the depressions of said two halves of said ceramic shape;at least projecting areas of said contacts being in said depression,said connections being connected to said contacts.